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UNITED STATES PATENT OFFICE.

MOMME ANDRESEN, OF BERLIN, GERMANY.

PROCESS OF DEVELOPING PHOTOGRAPHIC PICTURES.

SPECIFICATION forming part of Letters Patent No. 475,372, dated May 24,1892.

Application filed April 15, 1889. Serial No. 307,326. (No specimens.)Patented in Germany February 10, 1889, No. 50,265; in

Belgium March 26,1889, No. 85,558: in France March 26, 1889,110.196.980; in England March 26, 1889,1To. 5,207; in Norway March26,1889,N0.1,283; in$wedenMarcl1 26, 1889,No. 2,028 in ItalyMaroh81,1889, XXIII, 25,190, In 27: in Spain June 4, 1889, No. 9,408, and inAustria-Hungary February 20,1890,N0- 89,968 and No. 79

To all whom, it may concern.-

Be it known that I, MOMME ANDREsE chemist, a subject of the King ofPrussia, residing at 44 Melchiorstrasse, Berlin, Prussia, German Empire,have invented certain new and useful Improvements in and Relating to theDevelopment of Photographic Pictures, (for which Letters Patent havebeen obtained in Austria-Hungary, No. 39,968 and No. 79, dated February20, 1890; in Belgium, No. 85,558, dated March 26, 1889; in France, No.196,980, dated March 26, 1889; in Germany, No. 50,265, dated February10, 1889; in Great Britain, No.- 5,207, dated March 26,1889; in Italy,Vol. XXIII, 25,190, Vol. L, 27, dated March 31, 1889; in Norway, No.1,283, dated March 26, 1889; in Spain, No. 9,403, dated June 4, 1889',and in Sweden, No. 2,028, dated March 26, 1889;) and I do hereby declarethe following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

My invention relates to the development of photographic pictures bymeans of diamidonaphthaline, amido-naphthol, and dioxynaphthaline, aswell as their-sulpho-aoids.

As is well known in photography, it is the practice to treat thesensitive plates (prepared with chloride, bromide, or iodide of silver,or with two or all of these salts) after exposure with a developingsolution in order to bring to view the image produced on the sensitiveplate. The developing solution hitherto employed for this purpose hasusually consisted of a solution of oxalate of iron, sulphate of iron, orpyrogallic acid. Now I have found by experiment that a derivative ofnaphthaline, or of a naphthol, or their sulpho-acids as, for instance,diamido-naphthaline, amidonaphthol, and dioxynaphthaline, as well astheir sulpho-acids-gives much better results than the Well-knownalkaline pyrogallol developers, and are exceptionally suitable fordeveloping photographic pictures, whenever, in the production of suchpictures, a sensitizing agent is used that will be chemically affectedby the developer, as is the case in the use of a silver salt orsalts-for instance, the effect being to impart to the plate a blueblacktint similar to that produced when the picture is developed in a bath ofoxalate of iron, with the advantage that the sensitized plate is not inthe least colored. On the other hand, the developers forming thesubjectmatter of this invention are more durable in anaqueous alkalinesolution than the pyrogallol developers hitherto used. I thus obtain theadvantages possessed by known developing agents without theirdisadvantages.

A developing-bath prepared with my naphthol developer, in which it isintended to immerse the sensitive plate after having been exposed forthe purpose of producing a visible picture, is for instantaneousphotography advantageously composed of the following ingredients: fivegrams of the hereinbeforedescribed napthol developer, fifteen grams ofsulphite of soda, two hundred and fifty grams of distilled water, andfive grams of carbonate of potash. The above proportions can, however,be varied, or one or the other of the ingredients can be substituted byothers, providing the essential part-namely, the beforementioned naptholdeveloper-is contained in the developing-bath. Afterhavingimmersed thephotographic plate in this bath till the picture becomes completelydeveloped it is then fixed in the usual way.

Having thus described my invention, what I claim as new therein, anddesire to secure by Letters Patent, is-

1. In the art of photography, the improvement which consists insubjecting sensitized and exposed surfaces to the developing action of asolution of a derivative of naphthaline, substantially as set forth.

2. In the art of photography, the improvement which consists insubjecting sensitized and exposed surfaces to the developing action ofan alkaline solution of a derivative of naphthaline, substantially asset forth.

3. 111 the art of photography, the improvement which consists insubjecting sensitized and exposed surfaces to the developing action of asolution of diamido-naphthalinc, substantially as set forth.

4. In the art of photography, the improvement which consists insubjecting sensitized and exposed surfaces to the action of an alkalinesolution of diamido-naphthalinc, substantially as set forth.

5. A developing agent consisting of a solution of diamido-naphthalineand carbonate of n potash and sulphite of soda, substantially as setforth.

In testimony whereof I affix my signature in presence of two witnesses.

MOMME ANDRESEN. W itnesses:

B. R01, A. DUNCHIER.

